Individual spectacle lenses, in particular progressive individual spectacle lenses, have been described in numerous patent publications, for example in DE 197 01 312, DE 103 13 275, WO 01/81979, U.S. Pat. No. 6,871,955, or EP 0 880 046. They exhibit clearly better imaging properties than conventional spectacle lenses, since the individual situation of wear of the spectacle wearer is taken into consideration in the calculation and optimization.
As a rule, progressive spectacle lenses are optimized by minimizing a target function, in which target or target values for at least one optical variable (for example astigmatism and/or refractive power) or target or desired values for at least one aberration (for example astigmatic error or astigmatic deviation and/or refractive error) of the progressive spectacle lens are taken into account. The refractive error is the difference of the refractive power of the spectacle lens and the refractive power that is determined by refraction determination. Preferably, it is values in the position of wear of the spectacle lens, i.e. taking the system spectacle lens/eye into consideration.
The target or desired values of the at least one optical property (in particular the astigmatism) or of the at least one aberration (in particular the astigmatic deviation), which are taken into account in the target function, characterize the design of a spectacle lens. In addition, the spectacle lens design can comprise a suitable object distance model. For example, the object distance model can comprise an object distance function defined as the reciprocal object distance along the principal line. A standardized object distance model is indicated in DIN 58 208 part 2 (cf. image 6), for example.
A design of a spectacle lens can be characterized by several design parameters, such as the size and in particular the position of the viewing zones (distance, near, and intermediate or progression zones). The position of the viewing zones can be specified by the principal visual points (reference points distance and near), for example, which are then taken into account as parameters of the design. Further design parameters are the maximally admissible aberrations and/or gradients of the aberrations and/or parameters characterizing the object distance model, for example.
Moreover, progressive spectacle lenses can have different designs, for example depending on the main activities and other main applications. Thus, in addition to universal progressive spectacle lenses, manufacturers often also offer progressive spectacle lenses for the computer workplace, smaller spectacle lens frame, etc.